13 November 2006

I was listening to NPR a few weeks ago while pre-election news was still accosting my ears. Though not in my state (shockingly!), there was apparently a measure on the ballots in a lot of states referencing stem cell research. The title of the measure was, apparently, "Should any stem cell research be allowed?"

Okay, quick quiz: how did you first interpret that sentence? If you were in favor of certain varieties, but not all varieties of stem cell research, would you vote for it? In other words, does "any" mean "at least one type of" or "all types of"?

To me, and at least a few other people I've talked to, the prefered interpretation is "all"...it's also much easier to reach this interpretation if you put a bit of stress on "any." But it's also really easy to get the other interpretation by unstressing "any" or by putting another sentence in front of it (eg., "Stem cell research in all forms is purely evil." :P).

The strange thing is that I'm really having a hard time coming up with other examples where the preference for "all" is so strong (even with the stress). It seems that the fact that stem cell research is a class of things, rather than a single thing is important. It also seems that the presence of "should" is pretty much necessary. But even so, I really can't get anything else to come out with such a strong preference for "all".

So what does this have to do with NLP? Well, not too much other than language is hard. Something like this would probably kill a textual entailment system, but given that it's somewhat ambiguous even to people (the degree of ambiguity is person relative though: a Brit here tells me that he has a really hard time getting the "all" interpretation at all), maybe there's just nothing that can be done about it.

It's all in the context, Hal. Consider "Should any political refugee be granted asylum?" or "Should any frivolous lawsuit be given a hearing?" Stress certainly helps, but its complex, and different emphatic stresses on "any" could drive readings either way.

And while you may not want negation, the modal "should" is essentially providing the same service w.r.t. the syntax and semantics of "any". In fact, you only get the "some X" reading of "any X" in what are called "negative polarity contexts". Contrast "John ate anything" with the negative polarity example "John didn't eat anything".

As Hal notes, there's also complications from genericity. And sometimes it's hard to tell a generic from a hyperbolic universal. A statement like "John ate beans" can refer to a specific event, or it could refer to a generic state of being a bean-eater. For instance, you could say generically: "John ate beans as an infant, but hated them as a toddler" or specifically: "John ate beans for dinner Monday night, but not on Tuesday." The exercise is to substitute "anything" for "beans".

For those of you into translation, the even more interesting thing about negative polarity is that the rules vary by language, as do rules for stacking negations.

If you really like this kind of thing, check out my book on semantics; it covers these examples and dozens more, including interactions with negation, subject quantifiers, coordination, plurals (group and distributive), numerical modifiers, pied-piping, etc:Type-Logical Semantics, 1998, MIT Press.

I think you're exactly right. Everyone who is in favor of Adult Stem Cell Research, would say yes to the question "Are you in favor of any stem cell research." It is bureaucracy trying to justify spending money, even if the people don't agree. If they do agree, great, do it. But don't use vague, misleading terms to trick them into it.